#id -> #gdb_id

This pull changes the `id` attribute to `gdb_id`.

While this works in normal Ruby scripts, its generally a bad idea to overwrite `#id`. 

Mostly, I just found problems using this library inside of Rails because of this. It kept outputting the `#object_id`. No clue why its freaking out like that. I guess this is just why it's a bad idea to do.